1. Field
The present disclosure relates generally to manufacturing composite structures and, in particular, to inspecting composite workpieces during manufacturing. Still more particularly, the present disclosure relates to a method and apparatus for identifying contaminants on composite workpieces prior to curing the composite workpieces to form composite structures.
2. Background
Aircraft are being designed and manufactured with greater and greater percentages of composite materials. Composite materials are used in aircraft to decrease the weight of the aircraft. This decreased weight improves performance features such as payload capacities and fuel efficiencies. Further, composite materials provide longer service life for various components in an aircraft.
Composite materials are tough, light-weight materials created by combining two or more functional components. For example, a composite material may include reinforcing fibers bound in polymer resin matrix. The fibers may be unidirectional or may take the form of a woven cloth or fabric. The fibers and resins are arranged and cured to form a composite material.
Further, using composite materials to create aerospace composite structures potentially allows for portions of an aircraft to be manufactured in larger pieces or sections. For example, a fuselage in an aircraft may be created in cylindrical sections to form the fuselage of the aircraft. Other examples include, without limitation, wing sections joined to form a wing or stabilizer sections joined to form a stabilizer.
In manufacturing composite structures, layers of composite material are typically laid up on a tool. The layers may be comprised of fibers in sheets. These sheets may take the form of fabrics, tape, tows, or other suitable forms. In some cases, resin may be infused or preimpregnated into the sheets. These types of sheets are commonly referred to as prepreg.
The different layers of prepreg may be laid up in different orientations and different numbers of layers may be used depending on the thickness of the composite structure being manufactured. These layers may be laid up by hand or using automated lamination equipment such as a tape laminating machine or a fiber placement system.
After the different layers have been laid up on the tool, the layers consolidated and cured upon exposure to temperature and pressure, thus forming the final composite structure. Thereafter, the composite structure may be inspected to determine whether inconsistencies are present. The inspection may be performed using x-ray inspection systems, ultrasound inspection systems, and other types of non-destructive inspection systems.
If an inconsistency is identified, the composite structure may be reworked. In some cases, the inconsistency may result in the composite structure being discarded, requiring new composite structure to be manufactured. Examples of inconsistencies that may be present in a composite structure include voids, porosity, delamination, foreign object debris (FOD), and other types of inconsistencies.
Reworking parts or discarding and remanufacturing composite structures may delay the completion of an aircraft using the composite structures. Further, reworking or discarding parts may increase the cost in manufacturing aircraft by an undesirable amount.
Therefore, it would be desirable to have a method and apparatus that takes into account at least one of the issues discussed above as well as possibly other issues.